1. Technical Field
The present invention relates to a writing instrument for controlling ink supply to a writing element, and more particularly to a writing instrument and method of producing the same for controlling the ink supply by a gas enclosed in a blocking chamber with a small volume which has the gas such as air enclosed therein, and which is provided inside an ink supplying passage extending from an ink chamber to the writing element.
2. Background Art
In general, in a writing instrument of the type storing liquid ink in an ink chamber, it is necessary to control a flow amount and pressure of the ink being supplied from the ink chamber to a writing element. As the simplest type of such an ink control, there is a method for providing a porous member referred to as a relay core made of a bundle of fibers between an ink chamber and writing element, while pulling the ink out of the ink chamber by the capillary force of the relay core, and controlling a supply amount of ink by the resistance received by the ink flowing inside the relay core.
In addition, the capillary force exists in a writing element due to fine gaps between fibers when the writing element forms a so-called felt chip made of a bundle of fibers, or due to a fine gap between a ball and a ball holder when the writing element forms a ball chip. Such a capillary force causes the writing element to have an ink pulling force for pulling the ink and an ink holding force for holding the pulled ink.
Therefore, the above-mentioned control only by the relay core has not been able to stabilize the ink supply. That is, if the density of the relay core is reduced to decrease the flow resistance of the ink, when the writing instrument is not used for writing, the ink in the ink chamber is pulled out of the chamber by the ink pulling force of the writing element described above, and the writing element contains a large amount of the ink to be saturated, and becomes so-called ink rich state. As a result, a disadvantage arises that writing becomes undesirably thick at the beginning of the writing. Particularly in a ball chip using water-soluble ink, the ink pulling force and ink holding force have the hydraulic pressure head of only the order of a few ten to a hundred mm. Therefore, in a condition that this writing instrument is allowed to stand, i.e., that the ball chip is directed downward, it sometimes happens that a small amount of ink is pushed out of the gap between the ball and ball holder, due to the hydraulic pressure head of the ink existing in a portion from the ink chamber to the ball chip. When writing is started in such a condition, a disadvantage arises that a starting portion of the writing line becomes a shape of a comma (,).
In order to avoid the disadvantage, it is required to increase the density of the relay core to increase the capillary force and inner flow resistance, however, thus increasing causes the ink flowing inside the relay body to receive an excessive flow resistance. Hence, in the case of writing fast or the like, the supply of ink is insufficient, and a condition, so-called ink poor condition, occurs that an ink amount contained in the writing element is too small. As a result, a disadvantage may occur such that the writing becomes blurred.
In order to avoid the disadvantage, various ink control mechanisms have been considered conventionally. One of the mechanisms is to provide between an ink chamber and writing element a small mechanical valve mechanism that is opened by a predetermined pressure difference. In this mechanism, the valve mechanism is closed at the time the writing instrument is not used for writing, and thereby the ink is prevented from being supplied excessively to the writing element. Then, at the time the instrument is used for writing, the valve mechanism is opened due to a pressure difference caused by the ink pulling force of the writing element, and thereby the ink is supplied from the ink chamber to the writing element.
However, the above-mentioned valve mechanism is required to operate to be opened or closed by a small pressure difference of the hydraulic pressure head of the order of a few ten mm, and is further required to be formed to extremely small, and therefore has a disadvantage that the production, quality control and the like thereof become complicated. Further, in the case where the writing element forms the ball chip using water-soluble ink described previously, since the ink pulling force is low, the pressure for opening or closing such a valve mechanism should be set extremely finely, and thereby a disadvantage occurs that the production, quality control and the like thereof become complicated.
Further, as another ink control type, there is a so-called air chamber type in which a small chamber with air enclosed therein is provided between an ink chamber and a writing element. In general, when air exists in a liquid passage with a small cross-sectional area, a phenomenon, so-called vapor lock, occurs that the air becomes bubbles, thereby blockades the passage and blocks the flow of the liquid. The air chamber type uses the principle of this phenomenon to configure a kind of valve mechanism.
The air chamber type of instrument does not essentially require a mechanically movable portion such as a valve, and has advantages that the structure is simple and that the production is easy. However, the air chamber type of instrument naturally requires a mechanism for flowing the ink blocked by the internal bubbles at the time of writing, and therefore provides a problem that it is difficult to reserve the stability of the operation in the mechanism.
An example of the air chamber type of writing instrument is disclosed in U.S. Pat. No.3,397,939. In the writing instrument, a small chamber with air enclosed therein is formed in an ink passage provided between an ink chamber and a writing element, is opened in its upper portion into a passage which communicates with the ink chamber, and is filled in its lower portion with a porous filler which communicates with the side of the writing element.
In the instrument of the USP, when the instrument is not used for writing, the porous filler contains the ink to be almost saturated, and the air enclosed in the small chamber blocks the flow of ink. Then, when the ink contained in the filler is consumed by the writing and the porous filler becomes the ink poor condition, the air inside the small chamber is absorbed into the porous filler. Since the air inside the small chamber is thus absorbed into the filler, the ink flows into the small chamber from the above-mentioned passage, and is absorbed into the filler. Then, when the filler with the ink absorbed therein becomes the ink rich condition, the air absorbed into the filler is released to the small chamber to block the flow-in of the ink.
The instrument disclosed in the USP does not have a mechanically movable portion, has a simple structure, and is capable of controlling the flow of ink assuredly even when the ink pulling force of the writing element is low. However, a case sometimes occurs that the whole amount of air absorbed into the porous filler is not released when the ink is newly absorbed into the filler. Then, the air remaining in the filler flows as the ink in the filler flows by writing, and when the remaining air reaches the writing element, the ink pulling force of the writing element is decreased, and the writing becomes impossible or has an inconvenience.
In order to avoid the above-mentioned disadvantage, the instrument of the USP is configured so that the upper portion of the small chamber is formed in the shape of a cone, and that when the ink flows into the chamber from the passage communicating with the ink chamber, the ink drops along the inner periphery of the small chamber to be absorbed in the periphery of the filler filled in the lower portion of the small chamber. By such a configuration, the ink penetrates from the periphery to the center portion of the filler, and thereby the air absorbed in the filler collects towards the center portion to be released.
However, according to the experiment by the inventor of the present invention and others, in the instrument configured as described above, it was still difficult to release the whole amount of the air once absorbed into the porous filler by ink newly being absorbed, and further it was difficult to assuredly prevent the air from remaining in the filler.
The present invention has been carried out in view of the foregoing, and it is an object of the present invention to provide a writing instrument and method of producing the writing instrument which uses an air chamber type of ink control mechanism requiring no mechanically movable portion, having a simple structure, and operating to be opened and closed by small pressure difference, and which enables the mechanism for blocking and flowing ink by enclosed gas to provide high reliability.
A writing instrument of the present invention is provided with an ink chamber that stores ink, a writing element provided on a front end portion of the writing instrument, and an ink control mechanism provided between the ink chamber and the writing element, where the ink control mechanism comprises a blocking chamber with a gas housed therein, an ink-chamber-side passage for causing the blocking chamber to communicate with the ink chamber, a writing-element-side passage for causing the blocking chamber to communicate with the writing element, an ink storing portion formed in the blocking chamber to store and hold a small amount of ink while communicating with the writing-element-side passage, ink holding means for holding the ink entering the blocking chamber from the ink-chamber-side passage at a predetermined position in the blocking chamber, and ink relay means for transferring, when an amount of the ink held by the ink holding means is equal to or more than a predetermined amount, at least part of the held ink to the ink storing portion.
Thus, when the instrument is not used for writing, the gas, for example, air enclosed in the blocking chamber blocks the communication of the ink between the ink chamber and the writing element, and the ink is thereby prevented from being supplied undesirably to the writing element.
Then, when the ink is consumed by the writing, the ink stored in the ink storing portion is consumed, the volume of a spatial portion of the blocking chamber increases corresponding to the consumed amount of ink, and the air pressure inside the blocking chamber decreases. The ink thereby enters the blocking chamber from the ink-chamber-side passage, and the entering ink is temporarily held at the predetermined position by the ink holding means. When an amount of the ink held by the ink holding means exceeds the predetermined amount, the ink is transferred to the ink storing portion by the ink relay means. Ink is thereby stored again in the ink storing portion, whereby the gas pressure inside the blocking chamber returns to an initial state, and thereafter, the similar operation is repeated to supply the ink to the writing element.
This ink control mechanism is the air chamber type of ink control mechanism described previously, does not require a mechanically movable portion, and enables itself to assuredly operate to be opened and closed by small pressure difference. The block and communication of the ink by the enclosed air is performed by increase and decrease in the ink amount stored and held in the ink storing portion. Accordingly, it is not necessary to perform operations in the porous member for absorbing the air, causing the ink to penetrate, eliminating the air, etc., and therefore the mechanism has a reliable operation and a simple structure.
Further, according to a preferred embodiment, the blocking chamber has an inner diameter enabling the ink to be held in a liquid-cylindrical form in one end portion thereof, has a predetermined amount of a gas enclosed therein, and further has an ink relay body which projects into the blocking chamber from a side of the other end portion thereof, which communicates in its proximal end portion with the ink-chamber-side passage, which has a front end portion formed in a pointed shape being disposed adjacent a free surface of the ink held in a liquid-cylindrical form in the blocking chamber, and which transfers part of the ink to the writing-element-side passage by contacting the free surface.
Thus, when the instrument is not used for writing, the gas enclosed in the blocking chamber blocks the communication of the ink between the ink-chamber-side passage and the writing-element-side passage, and thereby the undesirable supply of the ink to the writing element is halted. Then, when the ink of the writing-element-side passage is consumed by the writing, the volume of a spatial portion of the blocking chamber increases corresponding to the consumed amount of ink, the enclosed gas pressure decreases to move the ink held in a liquid-cylindrical form, the free surface of the ink contacts the front end portion of the ink relay body, and thereby part of the ink is transferred to the writing-element-side passage. Thus, the volume of the spatial portion of the blocking chamber decreases to increase the gas pressure, the free surface of the ink held in a liquid-cylindrical form moves backward to be spaced apart from the front end of the ink relay body, and thereby the supply of the ink is halted. Accordingly, it is possible to supply the ink with the predetermined amount only when the instrument is used for writing.
Since the ink entering blocking chamber from the ink-chamber-side passage is held in a liquid-cylindrical form as described above, a clear free surface is formed in the front end portion of the ink. Further, since the front end portion of the ink relay body is formed pointedly, it is possible to dispose the front end portion adjacent the free surface of the ink held in a liquid-cylindrical form. Accordingly, when the ink of the writing-element-side passage is consumed even a little, the free surface contacts the front end portion of the ink relay body, and the ink is transferred to the side of the writing element. Therefore, the ink passage extending from the ink relay body to the writing element maintains the condition that the passage is always filled with the ink, and it does not happen that the gas of the blocking chamber enters the passage and is mixed with the ink. As a result, it is possible to assuredly prevent the gas from being transferred to the writing element with the ink.
Further, the producing method of the present invention comprises the steps of holding the writing instrument, provided with the ink control mechanism of dry condition with no ink contained therein, in a generally vertical posture with the writing element thereof directed downward, of injecting the ink into the ink chamber, of evacuating the gas in the blocking chamber through the ink relay means of dry condition by flowing the ink injected into the ink chamber to the ink holding means in the ink control mechanism, and of halting the evacuation of the gas through the ink relay means by flowing the injected ink to the ink relay means in the ink control mechanism, and thereby enclosing the gas with a predetermined amount remaining in the blocking chamber.
Accordingly, by a simple operation for holding the writing instrument of dry condition in a generally vertical posture and injecting the ink into the ink chamber, it is possible to accurately enclose a gas with a required predetermined amount in the blocking chamber, and to produce the writing instrument with accurate characteristics efficiently and assuredly.